Definition - What does Logarithm mean?
Logarithm is the opposite operation to exponentiation. The Logarithm of one number is exponent to the other fixed value that should be raised to produce the same number. In the simple cases it counts the repeated multiplication. Base 10 is a common Logarithm which has various applications in engineering and science. The number Logarithm contains alphabet letter "e" as its base and its use common in physics and mathematics due to its simpler derivative.
Petropedia explains Logarithm
Logarithms were introduced in the early 17th century by John Napier as an aid to simplify calculations. They were immediately adopted by scientists, engineers, navigators and many other people to do calculations more easily by using the Logarithm tables and slide rules. Whatever is present inside the logarithm is known as argument of the log. The endless multi-digit calculations and multiplication steps are replaced easily by simpler addition and table look-ups. Just like Logarithm is the inverse to exponentiation, complex Logarithms are the reverse functions of exponential functions. The other variant, discrete Logarithm is used in public-key cryptography.